arg-type in chained dict.get
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bug
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- Python
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Description
this is a relatively common working code:
d0 = {
"a":"x",
}
d1 = {
"b":"y",
}
def ff(x) -> str|None:
return d0.get(d1.get(x))
mypy reports
mypy.py:8: error: Argument 1 to "get" of "dict" has incompatible type "str | None"; expected "str" [arg-type]
dict.get is used specifically to handle missing data.
how would you "fix" this code?
Your Environment
Mypy version used: mypy 2.1.0 (compiled: yes)
Mypy command-line flags: --install-types --non-interactive --check-untyped-defs
Python version used: 3.14.5
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
No repository file or test is named. Reproduce the chained dict.get example with the stated Python version and mypy flags, then trace the type-checker path that emits the arg-type diagnostic. Done means establishing the expected behavior and documenting or regression-testing the result in the appropriate mypy test area.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Quiet
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100